1. Field of the Invention
This invention concerns filtering apparatus, and more particularly filtering arrangements including a drum filter submerged within a settling tank containing the liquid to be filtered, the liquid in the tank passing into an outer filter media layer on the drum filter to achieve filtration.
2. Description of the Prior Art
In filtration apparatus of the type described, it is necessary to establish a fluid connection between the drum filter and the remainder of the liquid circulation system to receive the filtered liquid. Such connection is desirably able to be readily made and unmade since the drums occasionally must be removed from the tanks for cleaning and other maintenance.
Since the drums are normally submerged in the tank, the making of such fluid connections is rather burdensome, particularly for the large filter sizes often used for industrial applications.
U.S. Pat. No. 4,407,720 granted to the present inventor describes a rotating drum filter of the type with which the present invention is concerned.
It has been heretofore known and practiced to establish a fluid connection by means of a sideways acting clamping mechanism which creates a loose sealing engagement with a opening in the side of the settling tank, the clamping mechanism being operable from above the liquid level in the tank. Such arrangements have been used for drum filters as well as for other type filter arrangements mounted within a settling tank.
The use of such clamping mechanism and sideways acting clamping mechanism adds to the expense and complication of the apparatus and also involves the making of the fluid connection by movement of the drum filter while submerged in the tank, which makes control over the drum motion cumbersome and uncertain.
In the filter arrangement according to U.S. Pat. No. 4,407,720 there is disclosed an improved backwash arrangement. The drum is formed by a series of circumferentially spaced but axially extending individual fluid passages, which are covered by a filtering layer of "wedge wire" or other filter media material, with the filtering flow drawing liquid through the outer filtering layer and into the axially extending individual passages. A backwashing flow is created successively through limited numbers of such passages at a time, such that filtering flow may continue through the remaining passages during backwashing flow through this limited number of passages, as described in detail in the aforementioned U.S. Patent.
This successive backwashing of limited areas of the drum surface media involves rotation of the drum, and as disclosed in the aforementioned U.S. Patent, an air motor and chain drive may be utilized.
In co-pending application, Ser. No. 520,184, filed on Aug. 4, 1983, there is disclosed a cylinder operated ratchet mechanism for producing incremental rotation of the drum. Such auxiliary mechanisms of course add to the expense and complexity of the filter apparatus. For low cost units it would be desirable to provide such indexing movement of the drum with only minimal apparatus.
Accordingly, it is an object of the present invention to provide an improved filtering apparatus of the type including a drum filter mounted within a settling tank in which a fluid connection may be established by a simple, reliable arrangement.
It is another object of the present invention to provide such filter arrangement in which the necessary fluid connection to the drum filter is established by the descending movement of the drum filtering upon lowering of the drum into a settling tank occurring when the drum is installed.
It is still another object of the present invention to provide an improved filter arrangement which does not require a sideways acting clamping mechanism.
It is yet another object of the present invention to provide an improved filter arrangement in which an indexing rotation of a rotary drum filter element is created without utilizing a separate drive mechanism.